Method and apparatus for reducing shoulder wear on testing wheel

ABSTRACT

The present invention includes methods and apparatus for testing tire performance using a laterally-contoured road wheel. Accordingly, particular embodiments of the machine include a wheel configured to rotate, the wheel having a tire operating surface configured to engage a tire during operation, the outer tire operating surface arranged along an annular side of the wheel and having a width extending laterally relative a circumferential direction of the wheel along a contoured path. The machine may further include a drive source configured to rotate the wheel and a tire mount configured to rotatably maintain a tire. The present invention also includes methods of forming a laterally-contoured tire operating surface for a road wheel.

This application claims priority to, and the benefit of, InternationalPatent Application No. PCT/US2011/067994, filed Dec. 29, 2011 with theUnited States Receiving Office, which is hereby incorporated byreference.

BACKGROUND OF THE INVENTION

This invention relates generally to road wheels for testing tires ontire testing machines and more specifically, to tire operating surfacesemployed by road wheels in testing or evaluating tire performance.

DESCRIPTION OF THE RELATED ART

Tires are often tested to determine any of a variety of characteristics.In particular instances, in lieu of testing tires on a vehicle, whereconditions are difficult to control, tires are tested on a rotating roadwheel to better control the test conditions. Such road wheels include anouter tire operating surface along which the tire contacts and operates.Such outer tire operating surface forms a radially outer surface of thewheel. It can also be said the outer tire operating surface is anannular surface.

In operation, the tire is forcefully applied against, and rotates along,the outer tire operating surface of the rotating road wheel. Althoughthe outer tire operating surface exhibits a curvature in a longitudinaldirection as the surface extends about a circumference of the wheel, theouter tire operating surface is laterally flat, whereby the surfaceextends laterally along a path perpendicular to the circumferentialdirection of the wheel and parallel to the rotational axis of the wheel.In other words, the outer tire operating surface of the wheel forms aright circular cylindrical surface extending laterally a constantdistance from relative the rotational axis of the wheel.

When a tire contacts a tire operating surface, whether it is a wheelsurface or a ground surface, a portion of the tire tread contacts theoperating surface. The portion of the tread contacting the operatingsurface forms an area of contact, which is referred to as a contactpatch or footprint of the tire. A tire footprint includes an outerperimeter defining the area of contact, which may form a particularshape.

One goal of tire testing machines is to closely replicate real-worldoperating conditions for tires, such as conditions where the tireoperates along a generally flat surface, such as a ground surface.Unfortunately, these cylindrical outer tire operating surfaces do notrepresent real-world conditions since it has been observed that tirestested on these cylindrical surfaces commonly exhibit notably higherwear on the shoulders of the tire treads than those tires tested on agenerally flat surface. In other words, the wear distribution across awidth of the tire tread is not representative of the wear distributionattained when the tire operates on a generally flat surface. It has alsobeen observed that a footprint of a tire tested on a cylindrical outerwheel surface is different than the tire footprint achieved whenoperating along a generally flat surface. A tire footprint is the areaof contact between a tire and a surface upon which the tire rests.

Therefore, there is a need to provide a road wheel having an outer tireoperating surface better representing real-world conditions, and inparticular, a wheel generating a wear distribution along a tire treadmore consistent with tires operating along a generally flat operatingsurface. There is also a need to generate a tire footprint moreconsistent with tires operating along a generally flat operatingsurface.

SUMMARY OF THE INVENTION

The present invention includes methods and apparatus for testing tireperformance using a wheel, the wheel having a laterally-contoured tireoperating surface. The present invention also includes methods offorming a laterally-contoured tire operating surface for a road wheel.In particular embodiments, such methods comprise a step of providing awheel configured to rotate, the wheel having an tire operating surfaceconfigured to engage a tire during operation, the tire operating surfacebeing arranged outwardly from a rotational axis of the wheel in a radialdirection of the wheel and having a width extending laterally relative acircumferential direction of the wheel, where the width of the operatingsurface extends laterally along a contoured path. Further steps of suchmethods include engaging forcefully a tread of a tire against the tireoperating surface of the wheel and rotating the tire and the wheel whileengaged according to the prior step for a sufficient duration toevaluate the tire.

In particular embodiments of the invention, a machine for testing tireperformance, the machine includes a wheel configured to rotate, thewheel having an tire operating surface configured to engage a tireduring operation, the tire operating surface being arranged outwardlyfrom a rotational axis of the wheel in a radial direction of the wheeland having a width extending laterally relative a circumferentialdirection of the wheel, where the width of the operating surface extendslaterally along a contoured path. Such embodiments include a drivesource configured to rotate the wheel and a tire mount configured torotatably maintain a tire and forcefully maintain the tire against thewheel.

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more detailed descriptionsof particular embodiments of the invention, as illustrated in theaccompanying drawings wherein like reference numbers represent likeparts of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a tire testing device comprising a machineincluding a road wheel upon which a tire operates to evaluate theperformance of the tire, the road wheel having a laterally-contouredouter tire operating surface forming a convex outer surface extendingannularly around the road wheel in accordance with a particularembodiment of the invention.

FIG. 2 is a sectional view taken along line 2-2 in FIG. 1, showing theconvex tire operating surface of the wheel engaging a tire.

FIG. 3 is a section view of a prior art road wheel engaging a tire, theouter tire operating surface of the road wheel comprising a rightcircular cylindrical surface.

FIG. 4 is a chart showing the leading edge of a tire footprint takenalong different tire operating surfaces.

FIG. 5 is a sectional view of an alternative embodiment of the roadwheel shown in FIG. 2, the alternative wheel comprising a laterallycontoured tire operating surface having a variable lateral curvature.

FIG. 6 is a sectional view of an alternative embodiment of the roadwheel shown in FIG. 2, the alternative wheel comprising a laterallycontoured tire operating surface having a variable lateral curvature.

FIG. 7 is a sectional view of an alternative embodiment of the roadwheel shown in FIG. 2, the alternative wheel comprising a laterallycontoured tire operating surface having a variable lateral curvature.

FIG. 8 is a sectional view of an alternative embodiment of the roadwheel shown in FIG. 2, the alternative wheel comprising a laterallycontoured tire operating surface arranged along an annular inner side ofthe wheel.

FIG. 9 is a top perspective view of a base member coated with adhesivebeing rotated along a single layer of aggregate arranged along aretention surface, the bonding surface of the base member and theadhesive layer being both laterally convex and longitudinally convex andthe single layer of aggregate and the retention surface being laterallyconcave according to a method of forming a tire operating surface for aroad wheel, in accordance with a particular embodiment of the invention.

FIG. 10A is an end elevational view showing the adhesive coated basemember being applied to a single layer of aggregate arranged along aretention surface in accordance with a particular embodiment of theinvention.

FIG. 10B is an end elevational view showing the adhesive coated basemember of FIG. 10A applied to the aggregate application fixture inaccordance with a particular embodiment of the invention.

FIG. 10C is a side elevational view of the adhesive coated base memberapplied to the aggregate application fixture showing the base memberbeing rotated along a length of the fixture in accordance withparticular embodiments of the invention.

FIG. 10D is a perspective view of a road wheel for use in tire testing,the road wheel having an external annular side including an annular tireoperating surface comprising a plurality of arcuate tire operatingsurface segments coated with aggregate in accordance with a particularembodiment of the invention.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

As suggested above, there is a need to provide an improved road wheelfor performing tire testing operations. With reference to FIG. 3, tireroad or testing wheels 118 employed in the prior art have an outer tireoperating surface 120 _(o)comprising right circular cylindricalsurfaces, whereby the outer tire operating surface is laterally flat. Inother words, the flat outer tire operating surface 120 _(o) generallyextends laterally across the surface width by being located a constantdistance R_(o) from a rotational axis A_(w)-A_(w) of the wheel such thatthe lateral extension of the outer surface 120 _(o) is parallel to therotational axis A_(w)-A_(w) (i.e., not inclined relative to therotational axis). The outer tire operating surface may include texture122, which may form a layer of particulate or other desirous material.However, when tires are tested on these right circular cylindricaloperating surfaces, the tire treads experience higher wear rates on thetread shoulders when compared to tires tested on a generally flatsurface. Furthermore, the shape of a tire footprint generated along aright circular cylindrical surface is notably different than the shapeof a tire footprint generated along a generally flat surface. Therefore,there is a need to provide a road wheel having a tire operating surfacethat better generates tread wear distributions across a tire footprintand a tire footprint more closely representing those obtained alonggenerally flat tire operating surfaces.

Accordingly, particular embodiments of the present invention comprisemethods of testing tire performance using a wheel having alaterally-contoured tire operating surface arranged along an annularside of the wheel. In testing tire performance, for example, tiredurability may be tested and evaluated. It is understood that thetesting of durability may evaluate the longevity of a tire tread byascertaining the rate of wear, but may also (additionally oralternatively) test the longevity of other elements of the tiresconstituent components. In any event, it may be desirous, when testing atire along a tire operating surface arranged along an annular side ofthe wheel, to better ensure that the tire wears as similar to a tireoperating on a generally flat surface, such as a ground surface or aflat machine testing surface. Likewise, it may be desirous, when testinga tire on such a tire operating surface of the wheel, to better ensurethat the tire has a footprint commensurate with the footprint of a tireoperating on a generally flat surface. Accordingly, an annular roadwheel is provided having a width extending laterally along a contouredpath to form a laterally-contoured tire operating surface arranged alongan annular side of the wheel. Accordingly, the tire operating surfacemay be arranged along an outer or inner annular side of the wheel, eachof which are arranged in a radial direction outwardly from therotational axis of the wheel. In certain embodiments, at least a portionof the laterally-contoured surface is convex, such as to form a roadwheel having a laterally-convex, outer tire operating surface. In yetother embodiments, the laterally-contoured surface is at least partiallyconcave. In particular embodiments, the wheel having laterally-contouredtire operating surface forms a portion of a tire testing machine. Thefollowing will now discuss various methods of testing tire performanceusing a wheel.

Particular embodiments of such methods include a step of providing awheel configured to rotate, the wheel having a tire operating surfacearranged along an annular side of the wheel and configured to engage atire during operation, the tire operating surface having a widthextending laterally relative a circumferential direction of the wheelalong a contoured path. In such embodiments, the wheel has alaterally-contoured tire operating surface configured to engage a tireduring operation. The tire operating surface is arranged along anannular side of the wheel and in a outwardly in radial direction fromthe rotational axis of the wheel. The annular side may comprise an inneror outer side of the wheel. Because the tire operating surface isarranged along an annular side of the wheel, when describing the shapeof either the tire operating surface or the tire operating side of thewheel, the description of one herein also describes the other unlessspecifically noted otherwise, and vice versa.

It is understood that the tire operating surface may extend continuouslyaround an annular side of the wheel to form an annular tire operatingsurface. In such instances, it can be said that the tire operatingsurface extends circumferentially about a rotational axis of the wheel.It is also understood that the tire operating surface may extenddiscontinuously or intermittently around an annular side of the wheel.In any event, the tire operating surface is a laterally-contouredsurface, extending laterally across a width of the surface transverse tothe radial direction of the wheel along a contoured path. The contouredpath may comprise any non-linear path, such as a contoured path, whichmay extend fully or partially across the width of the wheel.Accordingly, the laterally-contoured surface at least comprises anon-linear segment or portion, which may be coupled with one or morelinear segments or portions.

In particular embodiments, the laterally-contoured tire operatingsurface tapers radially inward toward the rotational axis of the wheelas the surface extends laterally outward relative a centerline of thetire operating surface, the centerline extending circumferentiallyaround the tire operating surface. In certain instances of suchembodiments, when the tire operating surface is arranged along an outerannular side of the wheel, the portion of the tire operating surfacetapering radially inward forms a convex tire operating surface.Accordingly, it can be said that the laterally-contoured tire operatingsurface extends laterally along a convex path to form a laterally-convexouter surface. In other instances of such embodiments, when the tireoperating surface is arranged along an inner annular side of the wheel,the portion of the tire operating surface tapering radially inward formsa concave tire operating surface. It is understood, however, thatlaterally-contoured inner and outer operating surfaces may each includeconcave and/or convex portions. Moreover, as otherwise noted herein, itis appreciated that the full width, or only a portion, of alaterally-contoured surface may be contoured. Accordingly, it can besaid that at least a portion of the width of the laterally-convexsurface extends along a convex or concave path. It is understood that aconvex tire operating surface is curved or rounded outwardly relativethe rotational axis of the wheel, whereby the lateral extents of thesurface width are located closer to the rotational axis of the wheelthan more intermediate portions of the surface width. For a concave tireoperating surface, the opposite is true. The convex, outer tireoperating surface provides a tread wear distribution across a tirefootprint more similar to the distribution attained when the tireoperates on generally flat surface. The convex, outer tire operatingsurface also provides a tire footprint that more closely resembles thetire footprint arising along a generally flat surface. The same benefitsappreciated for a convex, outer tire operating surface are alsoappreciated for a concave, inner tire operating surface.

It is understood that the laterally-contoured tire operating surface maybe symmetrical or asymmetrical relative a plane bisecting a width of thewheel and extending radially outward and normal to the rotational axisof the wheel (referred to herein as the “bisecting plane”). By furtherexample, the widthwise extension of the surface may extend along anynon-linear path, including a constant radius path or a path comprisingmultiple curved and/or linear segments defined by two or more differentradii, which may result in a curvilinear or non-linear path. Inparticular instances, the convexity or concavity of tire operatingsurface has a constant curvature defined by a constant radius ofcurvature. The origin of the radius of curvature may be located at anyradial or lateral location relative the rotational axis and thebisecting plane, respectively. For example, the origin of the radius ofcurvature may be located on the axis of rotation, on the bisectingplane, or may be spaced a desired distance from the axis of rotationand/or the bisecting plane. In more specific examples, the origin islocated at the intersection of the bisecting plane and the axis ofrotation. The resulting radius of curvature creates a spherical surface,although the surface does not extend 360 degrees around the origin. Itis possible to create more or less curvature by moving the origin closerto, or farther from, the axis of rotation. It is also possible toprovide asymmetry by moving the origin in a lateral direction away fromthe bisecting plane.

In performing tire performance testing, at least a portion of thelaterally-contoured tire operating surface may be texturized to includea texture. The texture may be provided to facilitate tire tractionand/or to facilitate tread wear. It is understood that such texture maycomprise any known or desired texture formed to or applied by anydesired process. For example, the texture may be formed into the tireoperating surface, such as by any manual or mechanized process, such asmolding, mechanical or chemical etching, cold or hot working, or anygrinding or abrasion process. Any such or otherwise desired texture maybe applied or attached to the tire operating surface, such as by way ofapplying a layer of desired material to the laterally-contoured surface.Exemplary texture includes texturized tape (such as safety walk tape),particulate, or stone, but may include any other material providing adesired texture upon which it is desired for a tire to operate whethernatural or unnatural. It is appreciated that the tire operating surfacemay have a smooth texture. It is noted that while the presence oftexture may provide a non-linear micro surface, the presence of suchtexture does not negate or alter the more generally formation of alaterally-contoured tire operating surface or side, and thelaterally-contoured path along which the tire operating surface or sideextends.

It is understood that the wheel may be formed in any manner and of anyconstruction. For example, the lateral-contour of a tire operatingsurface may be formed by molding or machining the convexity into thewheel's tire operating surface. By further example, such as when thetire operating surface is obtained by affixing one or more plates aroundthe outer or inner circumference of the wheel, the lateral-contour maybe achieved by molding, bending, or shaping each plate through any hotor cold forming process.

Further steps in performing the method of testing tire durability usinga wheel include (1) engaging forcefully the tread of the tire with thetire operating surface of the wheel and (2) rotating the tire and thewheel while engaged according to the prior step for a desired durationto evaluate the durability of the tire. Each of these steps may beperformed in accordance with known principles and techniques.

With regard to the step of engaging forcefully the tread of the tirewith the tire operating surface, tire and/or wheel may be translatedtoward the other to forcefully engage the tire and the wheel. Becausethe tire and wheel maybe mounted on the same machine, portions of themachine corresponding to the tire or wheel may translate to achieve suchengagement. Of course, the tire and wheel may be mounted on separatemachines or apparatus while still achieving the desired engagement. Itis also understood that any orientation of the tire relative the wheelmay be employed to provide any desired test condition. For example, byaltering the positional relationship between the rotational axes of thetire and wheel, a slip angle may be provided between the tire and wheelor camber introduced to the tire.

With regard to the step of rotating the tire and wheel, it is understoodthat the tire and/or wheel may be driven to accomplish the step ofrotating. In doing so, a drive source is arranged in operablecommunication with tire and/or the wheel. The drive source may compriseany drive source known to one of ordinary skill in the art, and maycomprise, for example, a motor.

These methods for testing tire durability on a laterally-contoured tireoperating surface may be achieved manually or automatically, in whole orin part. Exemplary embodiments of a tire testing device for use inperforming such methods are discussed in further detail below. Thedevice(s) shown in the figures only exemplify any of a variety of tiretesting devices that may be employed within the scope of this invention.

With reference to FIG. 1, an exemplary tire testing device 10 comprisinga tire testing machine is shown. The machine 10 includes a base orhousing 12 to which a tire 16 and a wheel 18 are rotatably attached(that is, configured to rotate). The tire testing device and housingincludes a tire mount configured to rotatably maintain a tire andforcefully maintain the tire against the wheel. A drive source 14 isalso included for driving the wheel and/or the tire, which may compriseany drive source known to one of ordinary skill in the art, such as amotor.

The wheel 18 includes a laterally-contoured outer side 19 _(o) generallyforming a laterally-contoured outer tire operating surface 20 _(g). Boththe outer side 19 _(o) and the outer surface 20 _(o) extend lengthwisein a circumferential direction about the wheel to form an annular sideand surface, respectively. Outer side 19 _(o) and outer surface 20 _(o)are shown to have a width W₁₈, which can be any size, including a sizeequal to or greater than the width W₁₆ of the tire 16. In the embodimentshown in FIG. 1, the outer surface 20 _(o) extends laterally in arounded or curved path to form a laterally-convex surface. This is moreclearly shown in FIG. 2, which shows a section of the wheel and tire ofFIG. 1 taken along line 2-2.

While it is understood that the laterally-convex surface may extendlaterally along any curved path, which may comprise any curvilinear ornon-linear path, the lateral path shown in FIG. 2 extends along aconstant curvature defined by a radius of curvature R_(c). Inparticular, radius R_(c) is shown extending from origin O. Although theorigin O may be arranged at any desired location, in the embodimentshown, the origin is arranged along a bisecting plane represented byline P-P. This bisecting plane P-P bisects the width W₁₈ of the outertire operating surface 20 _(o), and extends perpendicular to the wheel'srotational axis A_(w)-A_(w). It can be said that bisecting line P-Pdefines a lateral centerline of the wheel and/or of the outer tireoperating surface.

It is appreciated that origin O may be arranged any distance Δ_(rad)from the rotational axis A_(w)-A_(w) to achieve any desired radius ofcurvature R_(c). Accordingly, the curvature may be increased ordecreased by altering the distance Δ_(rad) between the origin O and therotational axis A_(w)-A_(w). For example, in FIG. 2, the origin O isshown arranged between the rotational axis A_(w)-A_(w) and the outersurface 20 _(o) arranged at the opposing end of the radius of curvatureR_(c). It is noted that the distance Δ_(rad) may be further increase theradius of curvature by positioning the origin beyond the rotational axisA_(w)-A_(w), whereby the rotational axis A_(w)-A_(w) is located betweenthe origin O and the outer tire operating surface 20 _(o) into which theradius of curvature R_(c) terminates. It is also appreciated that aspherical outer surface may be provided. For example, when Δ_(rad)equals zero, the origin O is arranged at the intersection of therotational axis A_(w)-A_(w) to form a spherical outer surface 20 _(o),that is a surface where the longitudinal and lateral extension of theouter surface extends the same distance from the origin. The outersurface may also be symmetrical relative bisecting plate P-P byarranging the origin O at the intersection of the rotational axisA_(w)-A_(w) and the bisecting plate P-P.

With continued reference to FIG. 2, the wheel's outer tire operatingsurface 20 _(o) is shown to be symmetrical relative to bisecting planeP-P or a circumferential centerline of the outer surface width W₁₈.Still, it is understood that outer surface 20 _(o) may be asymmetrical.When the lateral extension of outer surface is defined by a constantradius R_(c), such as is shown in FIG. 2, asymmetry may be achieved byaltering the distance between the origin O and the bisecting plane P-P.Alternatively or additionally, asymmetry may be achieved by defining thelateral extension or path of outer surface 20 _(o) with two or morelinear, curvilinear, or non-linear segments.

As noted otherwise herein, the outer tire operating surface may includetexture. With reference FIGS. 1 and 2, by example, the outer tireoperating surface 20 _(o) of wheel 18 includes texture 22. This texture22 is shown as a layer, but may comprise any desired texture formed orapplied to the outer surface 20 _(o) desired as more specificallydiscussed above.

As noted otherwise herein, the outer tire operating surface and/or sidemay extend in a widthwise direction of wheel along any desirednon-linear path, including any variable or multi-curvaturelaterally-contoured path. Exemplary embodiments thereof are shown inFIGS. 5-7, where the contoured path is defined by two or more differentradii of curvatures. In each figure, the tire is shown generally engagedwith the wheel; however, it is understood that the tire is often appliedunder load and therefore will deflect and therefore engage and operateconcurrently along a greater width of the wheel's outer surface. Withreference to FIG. 5, the laterally-contoured outer tire operatingsurface extends along a non-linear path including or defining a central,convex portion 24 (convex relative the outer side 19 _(o) of the wheel)arranged in an axial direction of the wheel between a pair ofcounter-curvature portions 26 having a radius of curvature R_(c). Byproviding counter-curvature portions 26, in effect, the outer tireoperating surface becomes flatter or less curved as the outer tireoperating surface extends laterally away from the centerline of thewheel. By doing so, the shape of a tire footprint may be bettercontrolled as the tire rolls along the tire operating surface and thecounter-curvature portion. It is noted that each of thecounter-curvature portions 26 are arranged adjacent the central, convexportion 24 to provide a smooth transition between the adjacent portions.It is understood that the pair of counter-curvature portions 26 may havethe same or different radii of curvature. It is further noted in theembodiment shown that the pair of counter-curvature portions define aconcave outer surface of the wheel.

In lieu of, or in addition to, employing a counter-curvature portion, alinearly-extending portion may extend from the central, convex portionas the outer tire operating surface extends toward a lateral side of thesurface width. In such instances, the provide a smooth transitionbetween the central portion and the linearly-extending portion, thelinearly-extending portion extends laterally an angle greater than zerorelative the rotational axis of the wheel. In any event, by providingcounter-curvature or a linear taper, any further increase in the slopeof the surface taper or curvature is eliminated as the tire operatingsurface approaches any lateral side of the wheel (or, in other words, asthe tire operating surface extends away from the centerline of thewheel).

By further example, with reference now to the embodiment of FIG. 6, eachcounter-curvature portion 26 extends further laterally, relative to theembodiment of FIG. 5, to form an upturn or raised area 28 at the lateralsides of the wheel. It can be said that while the central, convexportion 24 defines an area of decreasing outer diameter of the outertire operating surface 20 _(o) (relative the rotational axis A_(w)-A_(w)of the wheel 18 as the outer tire operating surface extends laterallyalong the width of the surface W₁₈), the upturn or raised area 28defines an area of increasing outer diameter for the outer tireoperating surface. With reference now to the embodiment of FIG. 7, inlieu of the counter-curvature 26 extending further laterally to form anupturn 28, a linearly-extending portion 30 is provided extendinggenerally parallel with the rotational axis A_(w)-A_(w) of the wheel 18.The linearly-extending portions 30 define cylindrical portions, whichmay form right-cylindrical surfaces as generally shown or any othertapered cylindrical surface as desired. Accordingly, the embodiment ofFIG. 7 provides an outer tire operating surface 20 _(o) extendinglaterally along a contoured path having a central, convex portion 24arranged between a pair of cylindrical portions 30.

As discussed otherwise herein, the tire operating surface may be formedalong an inner annular side of the wheel. By example, with reference toFIG. 8, a wheel 18 is shown having a tire operating surface 20 ₁arranged along an inner, annular side 19 ₁ of the wheel 18. A tire 16 isalso shown operating along the inner, annular side 19 ₁. In theembodiment shown, both the inner side 19 ₁ and the inner surface 20 ₁are laterally-contoured, and more specifically are concave (that is,concave relative the inner side 19 ₁). It is appreciated that the innerside 19 ₁ and the inner surface 20 ₁ may each extend laterally along anylateral contour and be texturized as contemplated herein for the outerside 19 _(o) and the outer surface 20 _(o). It is understood that afootprint formed along the inner side is generally longer relative afootprint formed along the outer side, for the same tire and surfaceshape. Therefore, it is believed that a concave surface, in lieu of aconvex surface employed by the outer side, or at the very least a radiusof curvature smaller than a radius of curvature employed by the outersurface, may be useful in shortening the footprint formed along theinner side to more closely achieve a footprint shape formed on a flatsurface.

As mentioned above, the present invention includes methods of forming alaterally-contoured tire operating surface for a road wheel. The tireoperating surface may be formed along an outer, annular side of the roadwheel, or may be formed along components for forming a road wheel havinga laterally-contoured operating surface. Exemplary embodiments forperforming these methods are shown in FIGS. 9-10C, where alaterally-contoured tire operating surface 50 having texture is formedas generally shown in FIG. 9 on a base member to form a componentcomprising one of a plurality of sections 44 that is subsequentlyattached to a road wheel as exemplarily shown in FIG. 10D having anannular tire operating surface. The process of forming the road wheelhaving a laterally-contoured tire operating surface is explained inassociation with a laterally-flat tire operating surface formed in FIGS.10A-10D, such that one of ordinary skill would understand that theprocess shown in FIGS. 10A-10D may be used to form a laterally-contouredtire operating surface by substituting the laterally-flat base memberwith a laterally-contoured base member to form any laterally-contouredoperating surface described herein.

With reference now to the exemplary embodiments of FIGS. 9-10D, the moregeneral methods of forming a laterally-contoured tire operating surfacefor a road wheel are discussed in association with the exemplaryembodiment shown therein, which is not limiting on the broader method offorming the laterally-contoured tire operating surface. With referenceto FIG. 9, methods of forming a laterally-contoured tire operatingsurface for a road wheel include the step of providing a longitudinallyconvex and laterally-contoured bonding surface 50 for receiving atextured tire operating surface 42 (shown in FIG. 10D), the bondingsurface being associated with a radially outer side 40 (shown in FIG.10D) of a rotatable road wheel 18 (shown in FIG. 10D) and having a widthextending widthwise along a contoured path and a convex length extendingalong an arcuate path. In the embodiment shown, the bonding surface 50forms a portion of a similarly shaped base member 46.

With reference to FIG. 10A, such methods further include the step ofapplying adhesive material 52 of a pre-determined thickness H₅₂ alongthe bonding surface 50 to form a coated bonding surface comprising alongitudinally convex and laterally-contoured layer of adhesive materialarranged along the bonding surface and arranging a single layer 60 ofaggregate material 58 along a retention surface 54, where each of thesingle layer of aggregate material and the retention surface are alsolaterally-contoured. Laterally-contoured variations of the coatedbonding surface, single layer of aggregate material, and retentionsurface are shown by example in FIG. 9.

With reference to FIG. 10B, such methods also include the step ofplacing a width of the layer of adhesive material 52 of the coatedbonding surface 50 into engagement with the single layer 60 of aggregate58. In the embodiment shown, aggregate guide members 56 are used to moreprecisely arranged the aggregates along the retention surface and tocontrol the engagement of the aggregate layer 60 with the coated bondingsurface 50. With reference to FIGS. 9 and 10C, the methods also includethe step of rotating the coated bonding surface 50 in a lengthwisedirection (in direction R) relative the retention surface 54 until alength of the convex layer of adhesive material has engaged the singlelayer 60 of aggregate 58, whereby the engaged aggregate remains affixedto the adhesive layer subsequent rotation to effectively transfer theengaged aggregate from the retention surface to the coated bondingsurface to coat the adhesive layer with aggregate and thereby affixingthe single layer of aggregate along the bonding surface to form a tireoperating surface 42 (shown in FIG. 10D) along the bonding surface.

To evaluate the benefits of using a laterally-contoured tire operatingsurface, laterally-contoured outer tire operating surfaces of differentradii were evaluated. In particular, tire footprints were taken alonglaterally-contoured outer tire operating surfaces and compared tofootprints taken along a laterally flat outer tire operating surface(being a common road wheel) and a flat surface representing a commonground surface. With reference to FIG. 4, a radial tire sized for a 16inch diameter rim and having a nominal width of 205 millimeters wastested on a flat surface and three different road wheels each having acircumferential diameter of 3 meters (m). The tire operating surface foreach road wheel was annular and symmetrical in a widthwise direction ofthe surface relative a plane extending through a circumferentialcenterline of the tire operating surface, the plane extendingperpendicular to the rotational axis of the road wheel and bisecting thetire operating surface along the maximum circumference of the tireoperating surface extending in a circumferential direction of the roadwheel. The first road wheel was laterally flat, meaning the tireoperating surface had a width extending parallel to the rotational axisof the road wheel to form a right circular cylindrical surface having a3 m diameter (where the tire operating surface was generally located 1.5m from a rotational axis of the wheel across the width of the surface).The tire operating surface of the second road wheel had alaterally-contoured surface, where the width of the tire operatingsurface extended laterally along a 1.5 m radius of curvature, the radiusextending from a location along the rotational axis of the road wheelwhere the radius of curvature defining the maximum circumference of thetire operating surface in a circumferential direction of the road wheeloriginates. The tire operating surface of the third road wheel had alaterally-contoured surface extending laterally along a 0.75 m radius ofcurvature in lieu of the 1.5 m radius of curvature characterizing thesecond road wheel. For each of the tests, a footprint was taken with thetire pressurized at 2.3 Bar (approx. equal to 33 pounds per square inch(psi) of pressure) and applied against the tire operating surface by a457 dekanewton force (approx. equal to 1027 pound-force).

With continued reference to FIG. 4, the leading edge of the eachfootprint measured on each tire operating surface detailed above isshown as a line or profile. The x-axis coordinate represents the lateralposition of the footprint's leading edge along a width of the footprintrelative a lateral centerline of the tire (where x=0). The lateralcenterline extends longitudinally along the length of the footprint todivide the width of the footprint into first and second halves. They-axis coordinate represents the length of the footprint and thedistance of the leading edge from a longitudinal centerline. Thelongitudinal centerline extends laterally across a width of thefootprint perpendicular to the lateral centerline of the tire to dividethe length of the footprint into first and second halves.

In FIG. 4, the leading edge profile of the footprint measured on theflat surface is identified as P_(FLT), while the leading edge profilemeasured for each footprint taken on the first road wheel (cylindricalsurface), the second road wheel (lateral radius of curvature equal to1.5 m), and the third road wheel (lateral radius of curvature equal to0.75 m) is identified as P_(CON), P_(H), and P_(r2), respectively.Generally, the smaller the radius of curvature, the greater thecurvature that is generated by the radius of curvature along the outertire operating surface. Upon review of the leading edge profiles foreach of the footprints measured, it is apparent that the length of eachfootprint formed along an annular outer tire operating surface (such ason a road wheel) is shorter than the footprint P_(FLT) formed on a flatsurface. It is also apparent that the prior art road wheel having acylindrical tire operating surface generates a footprint P_(CON) havingthe flattest leading edge and most unlike the footprint P_(FLT) formedalong a flat surface. With regard to the road wheels havinglaterally-contoured tire operating surfaces, it is shown that the roadwheel having a laterally-contoured surface defined by the smaller radiusof curvature generates a footprint P_(r2) having a longer length moreclosely approaching the length of the footprint formed on a flatsurface. This is an improvement over the footprint P_(CON) formed on theprior art road wheel having a cylindrical tire operating surface. It isalso shown that the road wheel having a laterally-contoured surfacedefined by the larger radius of curvature generates a footprint P_(r1)having a flatter-shaped leading edge more closely shaped to the leadingedge of the footprint formed on a flat surface. This is also animprovement over the footprint P_(CON) formed on the prior art roadwheel having a cylindrical tire operating surface.

While this invention has been described with reference to particularembodiments thereof, it shall be understood that such description is byway of illustration and not by way of limitation. Accordingly, the scopeand content of the invention are to be defined by the terms of theappended claims.

1. A method of testing tire performance using a wheel, the methodcomprising the steps of: providing a wheel configured to rotate, thewheel having a tire operating surface arranged along an annular side ofthe wheel and configured to engage a tire during operation, the tireoperating surface having a width extending laterally relative acircumferential direction of the wheel along a contoured path; engagingforcefully a tread of a tire against the tire operating surface of thewheel; and, rotating the tire and the wheel while engaged according tothe prior step for a sufficient duration to evaluate the tire.
 2. Themethod of claim 1, where the tire operating surface tapers radiallyinward toward the rotational axis of the wheel as the surface extendslaterally outward relative a centerline of the tire operating surface,the centerline extending circumferentially around the tire operatingsurface.
 3. The method of claim 1, where the width of the tire operatingsurface extends laterally along a convex path to form a laterally convextire operating surface.
 4. (canceled)
 5. The method of claim 1, wherethe contoured path is defined by a constant radius of curvature.
 6. Themethod of claim 2, where the convex path is defined by a constant radiusof curvature and the radius of curvature has an origin located at theintersection of the plane and the rotational axis of the wheel.
 7. Themethod of claim 2, where the convex path is defined by a constant radiusof curvature and the radius of curvature has an origin located along theplane and between the rotational axis of the wheel and the tireoperating surface.
 8. The method of claim 2, where the convex path isdefined by a constant radius of curvature and the radius of curvaturehas an origin located along the plane such that the rotational axis ofthe wheel is located between the tire operating surface and the origin.9. The method of claim 1, where the contoured path is defined by two ormore different radii of curvatures.
 10. The method of claim 1, where thecontour path provides a contoured portion arranged between a pair ofcylindrical portions.
 11. The method of claim 1, where the contouredpath defines a convex, central portion arranged between a pair ofcounter-curvature portions in an axial direction of the wheel, the pairof counter-curvature portions forming a concave side of the wheel.
 12. Amachine for testing tire performance, the machine comprising: a wheelconfigured to rotate, the wheel having a tire operating surface arrangedalong an annular side of the wheel and configured to engage a tireduring operation, the tire operating surface having a width extendinglaterally relative a circumferential direction of the wheel along acontoured path a drive source configured to rotate the wheel; a tiremount configured to rotatably maintain a tire and forcefully maintainthe tire against the wheel.
 13. The machine of claim 12, where the tireoperating surface tapers radially inward toward the rotational axis ofthe wheel as the surface extends laterally outward relative a centerlineof the tire operating surface, the centerline extendingcircumferentially around the tire operating surface.
 14. The machine ofclaim 13, where at least a portion of the width of the tire operatingsurface extends laterally along a convex path to form a laterally convextire operating surface.
 15. (canceled)
 16. The machine of claim 12,where at least a portion of the contoured path is defined by a constantradius of curvature.
 17. The machine of claim 14, where the convex pathis defined by a constant radius of curvature and the radius of curvaturehas an origin located at the intersection of the plane and therotational axis of the wheel.
 18. The machine of claim 14, where theconvex path is defined by a constant radius of curvature and the radiusof curvature has an origin located along the plane and between therotational axis of the wheel and the tire operating surface.
 19. Themachine of claim 14, where the convex path is defined by a constantradius of curvature and the radius of curvature has an origin locatedalong the plane such that the rotational axis of the wheel is locatedbetween the tire operating surface and the origin.
 20. The machine ofclaim 12, where the contoured path is defined by two or more differentradii of curvatures.
 21. The machine of claim 12, where the contouredpath provides a contoured portion arranged between a pair of cylindricalportions.
 22. The machine of claim 12, where the contoured path definesa convex, central portion arranged between a pair of counter-curvatureportions in an axial direction of the wheel, the pair ofcounter-curvature portions forming a concave side of the wheel.